Inflammatory pattern of the infrapatellar fat pad in dogs with canine cruciate ligament disease

Synergistic therapeutic effect of parecoxib and ilomastat combination in osteoarthritis via inhibition of IL-17/PI3K/AKT/NF-κB activity

BACKGROUND

Osteoarthritis is a degenerative disease, and current drug treatment is to give nonsteroidal anti-inflammatory drugs to relieve symptoms. The anti-inflammatory ability of parecoxib and ilomastat has been confirmed, but the synergistic effect of combined administration in osteoarthritis has not been clear.

METHODS

Mouse primary chondrocytes stimulated with IL-1β were cultured. The expression levels of inflammatory cytokines and matrix metalloproteinases were investigated by western blotting, quantitative real-time polymerase chain reaction and ELISA. The effects of parecoxib and ilomastat on chondrocyte apoptosis were evaluated by flow cytometry. In addition, the rat model of osteoarthritis was established by meniscal instability, and the morphological changes of cartilage and the expression levels of related molecules were monitored using Safranin O-Fast green and immunohistochemical staining after intra-articular injection of parecoxib, ilomastat, and the combination of the two.

RESULTS

In vitro experiments showed that the combined administration of parecoxib and ilomastat more effectively inhibited the expression of proinflammatory factors and matrix metalloproteinases compared with single drug administration. The combined drug treatment could more effectively inhibit IL-1β-induced chondrocyte apoptosis. The combined drug treatment alleviated the progression of osteoarthritis by inhibiting the IL-17/PI3K/AKT/NF-κB pathway. In addition, in vivo experiments showed that the combined administration could improve the further deterioration of the osteoarthritis rat model.

CONCLUSIONS

The combined administration of parecoxib and ilomastat to inhibit IL-17/PI3K/AKT/NF-κB transduction is beneficial to reduce the infiltration of inflammatory factors and matrix metalloproteinases in osteoarthritis.

Interleukin receptor therapeutics attenuate inflammation in canine synovium following cruciate ligament injury

OBJECTIVE

In the knee, synovial fibrosis after ligamentous injury is linked to progressive joint pain and stiffness. The objective of this study was to evaluate changes in synovial architecture, mechanical properties, and transcriptional profiles following naturally occurring cruciate ligament injury in canines and to test potential therapeutics that target drivers of synovial inflammation and fibrosis.

DESIGN

Synovia from canines with spontaneous cruciate ligament tears and from healthy knees were assessed via histology (n = 10/group) and micromechanical testing (n = 5/group) to identify changes in tissue architecture and stiffness. Additional samples (n = 5/group) were subjected to RNA-sequencing to define the transcriptional response to injury. Finally, synovial tissue samples from injured animals (n = 6 (IL1) or n = 8 (IL6)/group) were assessed in vitro for response to therapeutic molecules directed against interleukin (IL) signaling (IL1 or IL6).

RESULTS

Cruciate injury resulted in increased synovial fibrosis, vascularity, inflammatory cell infiltration, and intimal hyperplasia. Additionally, the stiffness of both the intima and subintima regions were higher in diseased compared to healthy tissue. Differential gene expression analysis showed that diseased synovium had an upregulation of immune response and cell adhesion pathways and a downregulation of Rho protein transduction pathways. In vitro application of small molecule therapeutics targeting IL1 (anakinra) or IL6 (tocilizumab) dampened expression of inflammatory and matrix deposition mediators.

CONCLUSION

Spontaneous cruciate ligament injury in canines is associated with synovial inflammation and fibrosis in a relevant model for testing emerging intra-articular treatments. Small molecule therapeutics targeting IL pathways may be ideal interventions for delivery to the joint space after injury.

Concurrent Joint Contact in Anterior Cruciate Ligament Injury induces cartilage micro-injury and subchondral bone sclerosis, resulting in knee osteoarthritis

Objective

Anterior Cruciate Ligament (ACL) injury initiates post-traumatic osteoarthritis (PTOA) via two distinct processes: initial direct contact injury of the cartilage surface during ACL injury, and secondary joint instability due to the ACL deficiency. Using the well-established Compression-induced ACL rupture method (ACL-R) and a novel Non-Compression ACL-R model, we aimed to reveal the individual effects of cartilage compression and joint instability on PTOA progression after ACL injury in mice.

Design

Twelve-week-old C57BL/6J male were randomly divided to three experimental groups: Compression ACL-R, Non-Compression ACL-R, and Intact. Following ACL injury, we performed joint laxity testing and microscopic analysis of the articular cartilage surface at 0 days, in vivo optical imaging of matrix-metalloproteinase (MMP) activity at 3 and 7 days, and histological and microCT analysis at 0, 7, 14, and 28 days.

Results

The Compression ACL-R group exhibited a significant increase of cartilage roughness immediately after injury compared with the Non-Compression group. At 7 days, the Compression group exhibited increased MMP-induced fluorescence intensity and MMP-13 positive cell ratio of chondrocytes. Moreover, histological cartilage degeneration was observable in the Compression group at the same time point. Sclerosis of tibial subchondral bone in the Compression group was more significantly developed than in the Non-Compression group at 28 days.

Conclusions

Both Compression and Non-Compression ACL injury initiated PTOA progression due to joint instability. However, joint contact during ACL rupture also caused initial micro-damage on the cartilage surface and initiated early MMP activity, which could accelerate PTOA progression compared to ACL injury without concurrent joint contact.

Expression of adipokines and adipocytokines by epidural adipose tissue in cauda equina syndrome in dogs

Background

Compression of epidural adipose tissue (EAT) within the scope of cauda equina syndrome (CES) could lead to an enhanced expression of inflammatory mediators, possibly contributing to pain amplification in dogs.

Objectives

To analyze expression of inflammatory adipo(‐cyto)kines within the EAT of dogs with CES.

Animals

Client‐owned dogs: 15 dogs with CES and 9 dogs euthanized for unrelated medical reasons (controls).

Methods

Prospective, experimental study. Epidural adipose tissue and subcutaneous adipose tissue were collected during dorsal laminectomy and used for real‐time quantitative polymerase chain reaction. Tissue explants were cultured for measurements of inflammation‐induced release of cytokines.

Results

Results show a CES‐associated upregulation of the cytokines tumor necrosis factor alpha (TNFα: mean ± SD: 18.88 ± 11.87, 95% CI: 10.90‐26.86 vs 9.66 ± 5.22, 95% CI: 5.29‐14.02, *: P = .04) and interleukin‐ (IL‐) 10 (20.1 ± 9.15, 95% CI: 14.82‐25.39 vs 11.52 ± 6.82, 95% CI: 5.82‐17.22, *: P = .03), whereas the expression of the adipokine leptin was attenuated in EAT of dogs with CES (3.07 ± 2.29, 95% CI: 1.80‐3.34 vs 9.83 ± 8.42, 95% CI: 3.36‐16.30, **: P = .007). Inflammatory stimulation of EAT explant cultures resulted in an enhanced release of IL‐6 (LPS: 5491.55 ± 4438, 95% CI: 833.7‐10 149; HMGB1: 1001.78 ± 522.2, 95% CI: 518.8‐1485; PBS: 310.9 ± 98.57, 95% CI: 228.5‐393.3, ***: P < .001).

Conclusion and Clinical Importance

Expression profile of inflammatory adipo(‐cyto)kines by EAT is influenced from compressive forces acting in dogs with CES and might contribute to amplification of pain.

Source and hub of inflammation: The infrapatellar fat pad and its interactions with articular tissues during knee osteoarthritis

Knee osteoarthritis, the most prevalent degenerative joint disorder worldwide, is driven by chronic low-grade inflammation and subsequent cartilage degradation. Clinical data on the role of the Hoffa or infrapatellar fat pad in knee osteoarthritis are, however, scarce. The infrapatellar fat pad is a richly innervated intracapsular, extrasynovial adipose tissue, and an abundant source of adipokines and proinflammatory and catabolic cytokines, which may contribute to chronic synovial inflammation, cartilage destruction, and subchondral bone remodeling during knee osteoarthritis. How the infrapatellar fat pad interacts with neighboring tissues is poorly understood. Here, we review available literature with regard to the infrapatellar fat pad's interactions with cartilage, synovium, bone, menisci, ligaments, and nervous tissue during the development and progression of knee osteoarthritis. Signaling cascades are described with a focus on immune cell populations, pro- and anti-inflammatory cytokines, adipokines, mesenchymal stromal cells, and molecules derived from conditioned media from the infrapatellar fat pad. Understanding the complex interplay between the infrapatellar fat pad and its neighboring articular tissues may help to better understand and treat the multifactorial pathogenesis of osteoarthritis.

Relationship of mRNA Expression of Selected Genes in Peripheral Blood and Synovial Fluid in Cranial Cruciate Ligament Deficient Stifles of Dogs

Simple Summary

The cranial cruciate ligament rupture is characterized by chronic inflammation, osteoarthritis of the stifle joint, and extracellular matrix degeneration of the ligament itself in dogs. Early pre-clinical cranial cruciate ligament alteration cannot be detected by clinical examination or standard radiography. Therefore, we assessed the possible relationship of inflammatory markers in peripheral blood and synovial fluid of affected stifle joints in comparison to a control. We also evaluated components of the extracellular matrix of ruptured ligaments and finally compared the tibial plateau angle and the anatomical-mechanical angle between groups. Some of the assessed inflammatory markers were significantly increased in both the peripheral blood and synovial fluid compared with the control, as were collagens. The tibial plateau angle was not significantly different; however, the anatomical-mechanical angle significantly increased in the ruptured ligaments. Our results suggest a possible positive relationship between inflammatory markers of blood and synovial fluid in cranial cruciate ligament deficient stifles compared to the control. These findings may support both local and systemic inflammation process at the same time during osteoarthritis progression. Based on this, it would be interesting to investigate the predictive osteoarthritis pathway of inflammatory cytokines, matrix metalloproteinases, and their effect on the extracellular matrix components of the cranial cruciate ligament in future studies.

Abstract

The cranial cruciate ligament rupture (CrCLR) is characterized by chronic inflammation and osteoarthritis (OA) of the stifle joint and extracellular matrix (ECM) degeneration of the ligament itself in dogs. Generally, OA may arise from chronic low-grade systemic inflammation. We assessed the possible relationship of inflammatory markers in the peripheral blood (PB) and synovial fluid (SF) of affected stifle joints in comparison to a control. Moreover, no study has shown the possible association between PB and SF levels of inflammatory markers in CrCLR stifles of dogs in veterinary medicine yet. We also evaluated components of ECM of CrCLR and finally compared the tibial plateau angle (TPA) and the anatomical-mechanical angle (AMA) between groups. Samples from PB and SF were examined for mRNA expression of interleukins, TNF-α and INF-γ. ECM components—collagen 1A1 and 3A1 and elastin—were examined for mRNA expression from SF. The level of relative expression for IL-1β, IL-8 and IFN-γ was significantly increased in both PB and SF in CrCLR stifles as compared with the control. Collagens were also significantly increased in CrCLR stifles. TPA was not significantly different; however, the AMA angle significantly increased in the CrCLR group. Our results suggest a possible relationship between PB and SF levels of inflammatory markers in CrCLR stifles of dogs.

Expression and biological functions of Ancylostoma ceylanicum saposin-like protein

Ancylostoma ceylanicum is a common zoonotic nematode that inhabits the small intestine of humans, dogs, and cats. Saposin-like proteins (SLPs) have hemolytic and antibacterial activities and could be used as diagnostic or vaccine candidates. To explore the biological functions of Ancylostoma ceylanicum SLP (Ace-SLP-1), cDNA-encoding Ace-SLP-1 mature peptide was cloned into prokaryotic expression vector pET-28a and transformed into Escherichia coli BL21 (DE3) to induce expression. After incubation of canine red blood cell suspension with different concentrations of recombinant Ace-SLP-1, the supernatant was separated to measure OD value and calculate the hemolysis rate. The different concentrations of recombinant protein were co-cultured with E. coli and Enterococcus faecalis, and colony-forming units (CFU) were determined by the plate counting method. Peripheral blood mononuclear cells (PBMCs) from healthy dogs were incubated with different concentrations of recombinant Ace-SLP-1, and the cytokine expression was evaluated by relative quantitative PCR. Our results showed that the hemolytic activity of Ace-SLP-1 increased with the increase in protein concentration from 25 to 100 μg/mL. The recombinant protein had no antibacterial activity against the two kinds of bacteria but could stimulate the secretion of cytokines (IL-4, IL-10, IL-12, and IL-13) in canine PBMCs. These data suggest that Ace-SLP-1 is involved in hookworm blood-feeding and survival and has good immunogenicity, supporting its potential as a diagnostic and vaccine target molecule.

Associations between early neutering, obesity, outdoor access, trauma and feline degenerative joint disease

OBJECTIVES

The aim of this case-control study was to identify early-life risk factors associated with the occurrence of owner-reported mobility changes in 6-year-old cats by examining prospective data from a longitudinal cohort study of pet cats, the Bristol Cats study.

METHODS

Data on potential risk factors were obtained from seven sequential questionnaires completed between the ages of 2-4 months and 5 years. Mobility-related questions from the study questionnaire distributed at the age of 6 years were used to calculate each cat's mobility score. Cats with mobility scores of ⩾2 and 0 were allocated to the case and control groups, respectively, and the cat's status was the outcome variable.

RESULTS

Of the 799 cats included for analysis, 238 (29.8%) had owner-reported mobility changes. Binomial logistic regression using backwards elimination identified four risk factors for owner-reported mobility changes at 6 years of age: entire neuter status at 6 months of age (odds ratio [OR] 1.97; 95% confidence interval [CI] 1.26-3.07), sustained trauma before 6 years of age (OR 1.85; 95% CI 1.30-2.60), outdoor access at 6 years of age (OR 1.67; 95% CI 0.96-2.90) and overweight/obese status at 6 years of age (OR 1.62; 95% CI 1.13-2.33).

CONCLUSIONS AND RELEVANCE

Risk factor analysis demonstrated that obesity, outdoor access and a history of trauma may predispose cats to developing owner-reported mobility changes associated with degenerative joint disease, whereas neutering before 6 months of age appears to decrease that risk.

Synovial fluid lubricin increases in spontaneous canine cruciate ligament rupture

Lubricin is an important boundary lubricant and chondroprotective glycoprotein in synovial fluid. Both increased and decreased synovial fluid lubricin concentrations have been reported in experimental post-traumatic osteoarthritis (PTOA) animal models and in naturally occurring joint injuries in humans and animals, with no consensus about how lubricin is altered in different species or injury types. Increased synovial fluid lubricin has been observed following intra-articular fracture in humans and horses and in human late-stage osteoarthritis; however, it is unknown how synovial lubricin is affected by knee-destabilizing injuries in large animals. Spontaneous rupture of cranial cruciate ligament (RCCL), the anterior cruciate ligament equivalent in quadrupeds, is a common injury in dogs often accompanied by OA. Here, clinical records, radiographs, and synovial fluid samples from 30 dogs that sustained RCCL and 9 clinically healthy dogs were analyzed. Synovial fluid lubricin concentrations were nearly 16-fold greater in RCCL joints as compared to control joints, while IL-2, IL-6, IL-8, and TNF-α concentrations did not differ between groups. Synovial fluid lubricin concentrations were correlated with the presence of radiographic OA and were elevated in three animals sustaining RCCL injury prior to the radiographic manifestation of OA, indicating that lubricin may be a potential biomarker for early joint injury.

The role of macrophages in osteoarthritis and cartilage repair

Osteoarthritis (OA) is a family of degenerative diseases affecting multiple joint tissues. Despite the diverse etiology and pathogenesis of OA, increasing evidence suggests that macrophages can play a significant role in modulating joint inflammation, and thus OA severity, via various secreted mediators. Recent advances in next-generation sequencing technologies coupled with proteomic and epigenetic tools have greatly facilitated research to elucidate the embryonic origin of macrophages in various tissues including joint synovium. Furthermore, scientists have now begun to appreciate that macrophage polarization can span beyond the conventionally recognized binary states (i.e., pro-inflammatory M1-like vs anti-inflammatory M2-like) and may encompass a broad spectrum of phenotypes. Although the presence of these cells has been shown in multiple joint tissues, additional mechanistic studies are required to provide a comprehensive understanding of the precise role of these diverse macrophage populations in OA onset and progression. New approaches that can modulate macrophages into desired functional phenotypes may provide novel therapeutic strategies for preventing OA or enhancing cartilage repair and regeneration.

Effect of Ancylostoma ceylanicum hookworm platelet inhibitor on platelet adhesion and peripheral blood mononuclear cell proliferation

Ancylostoma ceylanicum is a zoonotic parasitic nematode that can cause iron-deficiency anemia and malnutrition in humans. A. ceylanicum hookworm platelet inhibitor (Ace-HPI) can inhibit platelet aggregation in the host to facilitate blood sucking, but whether it possesses platelet adhesion inhibitory activity or immunomodulatory role is yet unknown. To explore the effect of Ace-HPI on platelet adhesion, we expressed the recombinant protein in two competent cells, BL21 (DE3) and Rosetta-gami2 (DE3), and incubated this protein with canine platelets in a 96-well microplate. Ace-HPI was used to stimulate peripheral blood mononuclear cells (PBMC) in vitro to investigate the effect on PBMC proliferation and cytokine expression. Results showed that Ace-HPI expressed in Rosetta-gami2 (DE3) strain was mostly soluble. The inhibitory effect of this protein on platelet adhesion was relatively weak (7-8%). This protein stimulated the proliferation of PBMC and promoted the expression of Treg and Th2 cytokines, such as IL-10 and IL-13. These results lay a foundation for exploring the role of Ace-HPI in hookworm disease pathogenesis and as a candidate molecule for hookworm vaccines.

The Role of Inflammation in the Pathogenesis of Osteoarthritis

A joint is the point of connection between two bones in our body. Inflammation of the joint leads to several diseases, including osteoarthritis, which is the concern of this review. Osteoarthritis is a common chronic debilitating joint disease mainly affecting the elderly. Several studies showed that inflammation triggered by factors like biomechanical stress is involved in the development of osteoarthritis. This stimulates the release of early-stage inflammatory cytokines like interleukin-1 beta (IL-1β), which in turn induces the activation of signaling pathways, such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), phosphoinositide 3-kinase/protein kinase B (PI3K/AKT), and mitogen-activated protein kinase (MAPK). These events, in turn, generate more inflammatory molecules. Subsequently, collagenase like matrix metalloproteinases-13 (MMP-13) will degrade the extracellular matrix. As a result, anatomical and physiological functions of the joint are altered. This review is aimed at summarizing the previous studies highlighting the involvement of inflammation in the pathogenesis of osteoarthritis.

Genetic mapping of distal femoral, stifle, and tibial radiographic morphology in dogs with cranial cruciate ligament disease

Cranial cruciate ligament disease (CCLD) is a complex trait. Ten measurements were made on orthogonal distal pelvic limb radiographs of 161 pure and mixed breed dogs with, and 55 without, cranial cruciate partial or complete ligament rupture. Dogs with CCLD had significantly smaller infrapatellar fat pad width, higher average tibial plateau angle, and were heavier than control dogs. The first PC weightings captured the overall size of the dog’s stifle and PC2 weightings reflected an increasing tibial plateau angle coupled with a smaller fat pad width. Of these dogs, 175 were genotyped, and 144,509 polymorphisms were used in a genome-wide association study with both a mixed linear and a multi-locus model. For both models, significant (p_genome <3.46×10⁻⁷ for the mixed and< 6.9x10^-8 for the multilocus model) associations were found for PC1, tibial diaphyseal length and width, fat pad base length, and femoral and tibial condyle width at LCORL, a known body size-regulating locus. Other body size loci with significant associations were growth hormone 1 (GH1), which was associated with the length of the fat pad base and the width of the tibial diaphysis, and a region on CFAX near IRS4 and ACSL4 in the multilocus model. The tibial plateau angle was associated significantly with a locus on CFA10 in the linear mixed model with nearest candidate genes BET1 and MYH9 and on CFA08 near candidate genes WDHD1 and GCH1. MYH9 has a major role in osteoclastogenesis. Our study indicated that tibial plateau slope is associated with CCLD and a compressed infrapatellar fat pad, a surrogate for stifle osteoarthritis. Because of the association between tibial plateau slope and CCLD, and pending independent validation, these candidate genes for tibial plateau slope may be tested in breeds susceptible to CCLD before they develop disease or are bred.